EFFECT OF INSULIN ON REGIONAL VASCULAR RESISTANCES IN CONSCIOUS RATS

In the rat, but not in humans and other mammals, chronic administratio n of insulin produces hypertension. The present aim was to determine t he effect of acute insulin infusion on regional vascular resistances a nd to determine the neurogenic contribution to the response. Conscious rats were infused with insulin (2 or 6 mU/min) before and after gangl ionic blockade with chlorisondamine (5 mg/kg). The low dose of insulin produced an increase in arterial pressure and hindquarter vascular re sistance; the high dose produced a gradual decrease in arterial pressu re and renal resistance. After ganglionic blockade, the hindquarter va soconstriction produced by the low dose was abolished. The high dose o f insulin produced both hindquarter and renal vasodilation. Thus the l ow dose of insulin had a selective neurogenic vasoconstrictor effect i n rat skeletal muscle vascular beds. With higher doses, direct vasodil atory effects in both skeletal muscle and renal vascular beds appeared . This greater sensitivity of the sympathoexcitatory effects of insuli n in rats may explain the ability of chronic insulin infusions to incr ease blood pressure in this species.